Biomedical subjects

A Li

Publications and source records attributed to A Li.

At least 199 records · Page 11Linked to original sources

PubMed1997

Vasoactive intestinal polypeptide enhances the GABAergic synaptic transmission in cultured hippocampal neurons.

The whole-cell mode of patch-clamp techniques was used to investigate the effect of vasoactive intestinal polypeptide (VIP) on spontaneous gamma-aminobutyric acid (GABA)-mediated inhibitory postsynaptic currents (IPSCs) of cultured hippocampal neurons. Application of VIP caused a significant increase in the frequency of spontaneous IPSCs with a reversible and dose-dependent manner. VIP had no effect on the mean amplitude and kinetic parameters of spontaneous IPSCs. In the presence of tetrodotoxin, VIP increased the frequency of miniature inhibitory postsynaptic currents (mIPSCs) without affecting their mean magnitude. Forskolin, but not its inactive analog 1,9-dideoxyforskolin, mimicked the stimulatory effect of VIP on spontaneous IPSCs and mIPSCs. VIP and forskolin failed to modulate GABAergic IPSCs in the presence of Rp-cAMPs, a cell permeable antagonist of cAMP-dependent protein kinase (PKA). Calcium channel blocker CdCl2 did not prevent VIP and forskolin from increasing the frequency of mIPSCs. These results suggest that the activation of presynaptic VIP receptor enhances the GABAergic synaptic transmission in cultured hippocampal neurons through the cAMP-PKA pathway and that VIP is likely to increase GABA release by directly stimulating the vesicular release apparatus.

2-Amino-5-phosphonovalerate↗

PubMed1997

Mechanisms underlying segmentation of colored textures.

This paper examines the nature of the post-receptoral chromatic and achromatic mechanisms involved in a texture segmentation task. Observers viewed a 64 x 64 square-element texture in which the chromaticity and brightness of each element was drawn from a one-dimensional Gaussian distribution of values centered at a white point in color space. The orientation in color space and variance of this distribution defined the noise in the stimulus. The mean chromaticity and/or brightness of a central 32 x 32 element area (the target) was shifted away from the white point along the same direction as the noise or along a different direction. We measured target thresholds as a function of noise amplitude. The steepness of this relationship defined the effectiveness of the noise. Within planes spanned by the achromatic axis and one of the two cardinal chromatic axes, we found selective effects of noise along each of the two cardinal axes. Within the purely chromatic (isoluminant) plane, we found selective effects of noise along four lines--the two cardinal chromatic axes and two intermediate ones. We describe a simple model to account for our results.

Color Perception↗

PubMed1997

Silicate core-organic refractory mantle particles as interstellar dust and as aggregated in comets and stellar disks.

The principal observational properties of silicate core-organic refractory mantle interstellar dust grains in the infrared at 3.4 microns and at 10 microns and 20 microns are discussed in terms of the cyclic evolution of particles forming in stellar atmospheres and undergoing subsequent accretion, photoprocessing and destruction (erosion). Laboratory plus space emulation of the photoprocessing of laboratory analog ices and refractories are discussed. The aggregated interstellar dust model of comets is summarized. The same properties required to explain the temperature and infrared properties of comet coma dust are shown to be needed to account for the infrared silicate and continuum emission of the beta Pictoris disk as produced by a cloud of comets orbiting the star.

Cosmic Dust↗

PubMed1997

Apparent mineralocorticoid excess in a Brazilian kindred: hypertension in the heterozygote state.

BACKGROUND: Apparent mineralocorticoid excess (AME) is a cause of low-renin, low-aldosterone hypertension in which cortisol acts as a mineralocorticoid. The condition reflects an inability to inactivate cortisol to cortisone due to defective activity of the type 2 isozyme of 11beta-hydroxysteroid dehydrogenase (11beta-HSD2). Homozygous mutations in 11beta-HSD2 gene in patients with AME have been described. A 7-year-old Brazilian girl had previously been found to have AME. Her father recently presented with mineralocorticoid hypertension at age 38 years. OBJECTIVE: To describe the clinical details, to perform steroid analyses and to assess the molecular basis for the hypertension in this kindred. METHODS: The 11beta-HSD2 gene was amplified from genomic DNA by the polymerase chain reaction and sequenced by direct chain-termination sequencing on an automatic DNA sequencer. The sequencing results were validated by restriction-site polymorphism. The mutant 11beta-HSD2 protein was expressed in Chinese hamster ovary polyoma cells and enzymatic activity was assessed by metabolizing cortisol in vitro. RESULTS: Sequence analysis of genomic DNA revealed a novel C1061T point mutation in exon V of the human 11beta-HSD2 gene, resulting in an amino acid substitution of alanine by valine at codon 328 of the enzyme protein (A328V). Expression studies confirmed that the mutant protein was devoid of 11beta-HSD2 activity. A HhaI restriction-site polymorphism confirmed that the proband was homozygous for the mutation whereas both parents were heterozygotes. The father of the proband had hypertension, a normal serum potassium level, suppressed plasma renin activity and plasma aldosterone level and a moderately elevated urinary cortisol: cortisone metabolite ratio. CONCLUSIONS: AME in this kindred is caused by a novel mutation in the 11beta-HSD2 gene. Detection of hypokalaemia, at least in this kindred, is an insensitive screening test for mineralocorticoid-based hypertension. In contrast to results from previously investigated kindreds, we have demonstrated that this kindred has an abnormal phenotype in the heterozygote state. Further studies are now required in order to evaluate the role of 11beta-HSD2 activity in the pathophysiology of 'essential' hypertension.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1997

Atopy phenotype in subjects with variants of the beta subunit of the high affinity IgE receptor.

BACKGROUND: Fc epsilon RI plays a central role in atopy, thus genetic variants of Fc epsilon RI-beta may alter receptor function to enhance atopic responses and may manifest as a more severe atopic phenotype and more symptomatic atopic disease. The immunological and clinical features of atopy in children with and without the Leu 181 variant of Fc epsilon RI-beta were compared. METHODS: Sixty British nuclear families, including 10 families with the Fc epsilon RI-beta variant Leu 181, recruited via a young proband with atopic asthma were analysed for atopic parameters including total IgE, specific IgE, and clinical atopic disorder. RESULTS: Compared with other children (combined atopic and non-atopic subjects), maternally inherited Leu 181 was associated with increased levels of total IgE (odds ratio (OR) 4.82, 95% confidence interval (CI) 1.02 to 27.66, p < 0.01) and a positive IgE response to grass pollen allergen (OR 7.45, 95% CI 1.56 to 35.52, p < 0.005) but not wheeze (OR 1.97, 95% CI 0.56 to 7.69), asthma (OR 2.25, 95% CI 0.65 to 7.85), or required medications (OR 0.95, 95% CI 0.29 to 3.14). There were trends for each atopic parameter to be more marked in atopic children with maternally inherited Leu 181 than in atopic children without Leu 181. Children with maternal Leu 181 had significantly raised eosinophils but there was no difference in basophil levels compared with other atopic children. CONCLUSIONS: The Leu 181 variant of Fc epsilon RI-beta, or another identified variant in linkage disequilibrium, may promote the development of atopy.

Adolescent↗

PubMed1997

Effects of unilateral lesions of retrotrapezoid nucleus on breathing in awake rats.

In anesthetized rats, unilateral retrotrapezoid nucleus (RTN) lesions markedly decreased baseline phrenic activity and the response to CO2 (E. E. Nattie and A. Li. Respir. Physiol. 97:63-77, 1994). Here we evaluate the effects of such lesions on resting breathing and on the response to hypercapnia and hypoxia in unanesthetized awake rats. We made unilateral injections [24 +/- 7 (SE) nl] of ibotenic acid (IA; 50 mM), an excitatory amino acid neurotoxin, in the RTN region (n = 7) located by stereotaxic coordinates and by field potentials induced by facial nerve stimulation. Controls (n = 6) received RTN injections (80 +/- 30 nl) of mock cerebrospinal fluid. A second control consisted of four animals with IA injections (24 +/- 12 nl) outside the RTN region. Injected fluorescent beads allowed anatomic identification of lesion location. Using whole body plethysmography, we measured ventilation in the awake state during room air, 7% CO2 in air, and 10% O2 breathing before and for 3 wk after the RTN injections. There was no statistically significant effect of the IA injections on resting room air breathing in the lesion group compared with the control groups. We observed no apnea. The response to 7% CO2 in the lesion group compared with the control groups was significantly decreased, by 39% on average, for the final portion of the 3-wk study period. There was no lesion effect on the ventilatory response to 10% O2. In this unanesthetized model, other areas suppressed by anesthesia, e.g., the reticular activating system, hypothalamus, and perhaps the contralateral RTN, may provide tonic input to the respiratory centers that counters the loss of RTN activity.

Animals↗

PubMed1997

Focal central chemoreceptor sensitivity in the RTN studied with a CO2 diffusion pipette in vivo.

We describe and use a CO2 diffusion pipette to produce a quickly reversible focal acidosis in the retrotrapezoid nucleus region of the rat brain stem. No tissue injection is made. Instead, artificial cerebrospinal fluid (aCSF) equilibrated with CO2 circulates within the micropipette, providing a source for continued CO2 diffusion into the tissue from the pipette tip. Tissue pH electrodes show the acidosis is limited to 500 micron from the tip. In controls (aCSF equilibrated with air), 1-min pipette perfusions increased tissue pH slightly and decreased phrenic nerve amplitude. In moderate- and high-CO2 groups (aCSF equilibrated with 50 or 100% CO2), 1-min perfusions significantly decreased tissue pH and increased phrenic nerve amplitude in a dose-dependent manner. The responses developed and reversed within minutes. Compared with our prior use of medullary acetazolamide injections to produce a focal acidosis, in this approach the acidosis 1) arises and reverses quickly and 2) its intensity can be varied. This allows study of sensitivity and mechanism. We conclude from this initial experiment that retrotrapezoid nucleus region chemoreceptors operate within the normal physiological range of CO2-induced tissue pH changes.

Acetazolamide↗

PubMed1997

RTN TRH causes prolonged respiratory stimulation.

We injected thyrotropin-releasing hormone (TRH; 10 nl; 0.25, 0.5, 1.0, or 10 mM), its inactive free acid form (TRHOH; 1 mM), or a metabolite with low TRH-receptor binding affinity, histidine-proline diketopiperazine (cHP; 1 mM), into the retrotrapezoid nucleus of anesthetized rats. Injection location was verified by anatomic analysis. Lower doses (0.25-0.5 mM) significantly increased both the product of integrated phrenic amplitude and frequency (Phr . f) and f for 20-30 min compared with artificial cerebrospinal fluid control injections. Higher doses (1. 0-10 mM) produced greater and long-lasting stimulation of Phr . f, Phr, and f and of blood pressure. This stimulation reached values 150% of baseline and durations of 270 min after a single injection. TRHOH (1 mM ) or cHP (1 mM) had no effect on Phr but increased f, as did 1 mM TRH. We conclude that TRH has a very powerful stimulatory effect in the retrotrapezoid nucleus region on Phr . f, with the Phr response seemingly specific for TRH receptors. Similar responses of f to TRHOH and cHP suggest it may be nonspecific.

Animals↗

PubMed1997

A novel estrogen-enhanced transcript identified in the rat uterus by differential display.

Estrogen exerts its physiological effects in the uterus by inducing a cascade of transcriptional events; however, the number of genes known to be directly activated by estrogen in the uterus is small. In this study, immature ovariectomized rats were treated with estrogen or vehicle, and 3 h later the uterine horns were flushed to extract epithelial RNA. This RNA was used in the differential display technique to search for estrogen-responsive genes. Products of reverse transcriptase-PCR, made with pairs of arbitrary and oligo-deoxythymidine primers, were separated on denaturing polyacrylamide gels; candidate bands were excised and reamplified to produce probes for use in Northern blot analysis and screening of a lambda gt10 complementary DNA library made from rat uterus. A novel estrogen-enhanced transcript, designated EET-1, was identified from a differential display band, and the estrogen sensitivity of its expression was verified in Northern analysis. Characterization of EET-1 expression in the uterus showed that estrogen treatment resulted in a rapid and transient increase in EET-1 messenger RNA; steady state levels peaked between 2-3 h, returning to basal levels by 6 h. This increase was not abolished by pretreatment with cycloheximide, indicating that induction of EET-1 is a primary response to estrogen. Induction was specific to estrogen when extracts of whole uterus were examined; in the epithelium, there was also a slight response to progesterone. Expression of the gene was found in all organs surveyed; however, hormonal regulation was observed only in tissues of the reproductive tract and in the kidney. Analysis of cloned EET-1 complementary DNA revealed a 2008-base sequence that showed 61% identity with a reported transcript that encodes a protein that plays a role in phorbol ester-induced regulation of the tumor necrosis factor-alpha gene. Potential casein kinase-2 and protein kinase C phosphorylation sites and a cysteine-rich region were identified in the amino acid sequence deduced from EET-1. Thus, it appears that EET-1 represents a primary estrogen response gene that may code for a phosphorylated protein involved in gene regulation through a protein kinase C-activated pathway.

Amino Acid Sequence↗

PubMed1997

Automated differential display using a fluorescently labeled universal primer.

We have modified the automated differential display reverse transcription polymerase chain reaction technique (DDRT-PCR) such that a single fluorescently labeled universal primer (d(F)CTCACG-GATCCGTCGATTTT) is used in all PCRs together with a selection of arbitrary primers. We term this fluorescent detection procedure FDDRT-PCR. Anchoring primers of general structure dTGGTCTCACGGATCCTCGA-(T)12 VN (where N can be any deoxynucleoside and V can be any deoxynucleoside other than thymidine) are used for the RT step, and the universal primer together with selected arbitrary primers are then used for the PCR amplification. Advantages of this approach are: (i) the fluorescently labeled universal primer is a constant feature in every PCR, so that changes in banding profile are highly likely to reflect the incorporation of different arbitrary 10-mer primers; (ii) artifacts that result from arbitrary 10-mer to arbitrary 10-mer primer amplifications are not observed by fluoresence detection on an automated gene scanner because such products are not fluorescently labeled; (iii) sample throughput and ease of data handling are increased when compared with the conventional radioactive/manual approach and (iv) using a single fluorescently labeled primer in all PCRs is highly cost-effective.

Autoradiography↗

PubMed1997

[Clinicopathological study on 15 cases of pilomatrix carcinoma].

OBJECTIVE: To analyse the pathomorphology and the clinical biological behavior of pilomatrix carcinoma as well as to clarify the main points of diagnosis and differential diagnosis. METHODS: A review of the clinicopathological, histochemical and immunohistochemical features of 15 pilomatrix carcinomas a well as their clinical data was made. RESULTS: Of the 15 cases, 6 were male and 9 female, aged 11 to 83 (mean age 46 years). The tumor diameter varied from 1.2 cm to 8.0 cm (mean 3.5 cm). Histologically, pilomatrix carcinomas are characterized by sheets and islands of proliferating atypical baseloid cells with an infiltrating border. Transition to squamous, clear and ghost cell are often observed. The trichohyalin granules and tricholin-like acidophilic bodies are seen in tumor cells. Follow-up on 13 cases revealed local recurrence in 7 cases with multiple recurrence in 2 cases. One died of liver metastasis and one died of extensive local spread of the tumor. CONCLUSION: Pilomatrix carcinoma is a malignant tumor which usually recurs. Better curative results are obtained by wide excision.

Adolescent↗

PubMed1997

[A clinical study of early enteral feeding to protect the gut function in burned patients].

In order to investigate the effects of early enteral feeding on the gut after burn, 21 cases (mean burn area 45%) were randomly divided into early feeding group (EF group) and delayed feeding group (DF group). The results showed that the levels of plasma endotoxin and MDA in EF group were much lower on PBD 4, 8, 14 than those of DF group (P < 0.05-0.01), and plasma SOD was much lower in DF group on PBD 4, 8 (P < 0.01). The contents of serum gastrin and plasma motilin were obviously increased, and TNF IL-8 much lower in EF group at most time points (P < 0.05-0.01). Therefore, it seems that the early enteral feeding can decrease the level of plasma endotoxin in blood, reduce reperfusion injury of the gut, and blunt the chain reaction of "endotoxin-inflammatory mediator-gut mucosa injury."

Adolescent↗

PubMed1997

[Identification of the properties of haptoglobin-like substance in burn serum].

In our previous study, a haptoglobin-like substance possessing immunosuppressive activity was found in the sera of burned patients. However, its properties have not yet been clarified. In the present study, we mainly investigated the properties of the haptoglobin-like substance. The results showed that the abnormal protein bands identified by SDS-PAGE were the different subunits of haptoglobin, i.e., beta, alpha 2 and alpha 1 chains. The haptoglobin in burned sera was identical to that in normal sera in molecular weight, isoelectric point, hemoglobin-binding capacity and immunochemical properties as analyzed by SDS-PAGE, isoelectric focusing, immunochemical and biochemical methods. According to our results, it is suggested that the haptoglobin-like substance reported in the past is probably the haptoglobin, and that there may be no alteration in the properties of haptoglobin following burns.

Animals↗

PubMed1997

[Experimental study on the treatment of smoke inhalation injury with lung lavage and exogenous pulmonary surfactant].

To investigate the prevention and treatment effects of lung lavage and exogenous pulmonary surfactant (PS) on endogenous surfactant system dysfunction and acute respiratory failure caused by severe smoke inhalation, Wistar rats were randomly divided into five groups: Group I, normal control; Group II, smoke inhalation; Group III, smoke + lavage + PS + mechanical ventilation (MV); Group IV, smoke + lavage + MV; Group V, smoke + MV. The lungs were lavaged with 30 ml/kg 0.9% NaCl containing 100 mg/kg PS or same volume of saline via tracheal catheter at 5 min after smoke inhalation, then the animals were placed on a ventilator for 4 h, and observed until 24 h postinjury. The arterial blood gas levels, lung water volume, static lung compliance (Cst), total protein and albumin contents in bronchoalveolar lavage fluid (BALF), surface tension properties of BALF, and fatality rate at 24 h were measured. Smoke inhalation caused a similar acute hypoxia and severe carbon monoxide poisoning immediately in all injuried groups. The animals in group II showed acute respiratory failure, serious high permeability pulmonary edema, and surfactant system dysfunction. The surface tension properties of BALF, Cst, and the oxygenation were significantly improved with lung lavage and exogenous PS treatment. The lung water volume, total protein and albumin contents in BALF were decreased dramatically in this group. The fatality rate at 24 h declined markedly only in group III. It was suggested that lung lavage and exogenous surfactant treatment trestores effectively endogenous surfactant function inhibited by smoke inhalation, improves lung function, prevents high permeability pulmonary edema and respiratory failure, and decreases the mortality in early stage after smoke inhalation injury.

Animals↗

PubMed1997

[Anatomy of the cartilages of the nose with secondary deformity associated with unilateral cleft lip].

To explore the influence of displacement and hypoplasia of nasal cartilages to cleft lip nose, 38 patients with secondary cleft lip nasal deformity were randomly chosen. Measurement of length and width of the nasal cartilages was made, and places of them were inspected. The displacement of the cartilages was found in each nose, and hypoplasia of cartilages was in those noses whose deformities were more severe. The conclusion is that both displacement and hypoplasia of nasal cartilages are causing factors of nasal deformity.

Adolescent↗

PubMed1997

[Anatomy of the nasal cartilages of the unilateral lip and palate cleft nose].

Noses of 6 stillborn infants with unilateral lip and complete palate cleft were dissected and analysed. The surgical dissection revealed that the lower lateral cartilages are asymmetrical on both sides, indicating displacement of the lower lateral cartilages and the cartilageous septum which deviates to the normal side. Paired T Test shown that there is no significant difference between two sides in length and width. The conclusion is that the nasal deformities of the lip and palate cleft are congenital and one of the major causal factors is the displacement of lower lateral cartilages and cartilageous septum in the cleft side.

Abnormalities, Multiple↗

PubMed1997

[Evidence for a major role of genetic factors in the etiology of laryngeal and hypopharyngeal carcinomas].

Several investigations revealed that lymphocytes from patients with head and neck cancers showed a high sensitivity to mutagens. However, whether lymphocytes from healthy blood relatives of the patients were sensitive to mutagen or not had not been reported. This study was aimed to investigate the unknown problem. Mutagen sensitivity was investigated in 116 laryngeal and 38 hypopharyngeal cancer patients, 107 healthy controls, and 30 blood relatives of laryngeal or hypopharyngeal cancer patients. Chromosome damage was measured by enumerating mutagen-induced chromatid breaks, the average number of chromatid breaks per cell (b/c value) was used as marker which reflects variable host susceptibility to the action of environmental carcinogens. The b/c values were 0.61 +/- 0.27, 0.66 +/- 0.31, 0.28 +/- 0.12, and 0.45 +/- 0.26 for patients with laryngeal cancer, hypopharyngeal cancer, healthy controls, and blood relatives respectively. A significant difference of b/c value was found between patients and controls (P < 0.01), but not between patients and their blood relatives (P > 0.05). Our findings suggest that genetic predisposition plays an important role in the eitiology of laryngeal and hypopharyngeal cancers. Both patients with laryngeal or hypopharyngeal cancers and their blood relatives should be considered as in high cancer risk.

Aged↗

PubMed1997

[Relationship between human cytomegalovirus infection and soluble interleukin-2 receptor level].

In order to study the relationship between human cytomegalovirus infection and soluble interleukin-2 receptor (sIL-2R) level, 104 serum samples were selected from women of childbearing age in the city of Wuhan and examined with ELISA for anti-HCMV antibody IgG and IgM. Then we detected the sIL-2R level with double antibody ELISA in these sera with different conditions of HCMV infection. The results of different groups were compared with those women without cytomegalovirus infection and also compared with each other. The positive rate for anti-HCMV antibody IgG in the women of Wuhan was 89.4% (93/104) and for anti-HCMV antibody IgM only was 9.6% (10/104). The sIL-2R level of these women with HCMV infection was significantly higher than that in the control group (178.1 +/- 57.3 U/ml), P > 0.05. The highest level of sIL-2R were in those women whose anti-HCMV antibody IgM were positive (910 +/- 465.6 U/ml) and secondly was in those with anti-HCMV antibody IgG, IgM positive (905 +/- 347.8 U/ml). They were both higher than that in those women only with anti-HCMV antibody IgG positive (446.8 +/- 158.9 U/ml), P > 0.05. The results showed that HCMV infection can raise the sIL-2R level in serum of childbearing age women, especially in those with active HCMV infection. sIL-2R may be one of the pathogenic factors of HCMV.

Adult↗